1. Field of the Invention
This invention relates generally to resealable closures for beverage containers and, more specifically, to resealable closures that utilize a combination of initial mechanical interference and internal pressure to achieve and maintain a tight, reliable seal of a dispensing port of a beverage container.
2. Description of the Prior Art
Many inventions have been proposed to reseal a carbonated beverage container in order that a portion of the contents can be saved for a later time. In the case of beverage cans, most of these inventions have proposed using a variation on a bottle cork; i.e., they involve inserting some kind of stopper into the dispensing port created by pushing in a scored portion of the metal end at the time of initial opening. None of these inventions have been commercially successful. The problem is that the carbonated beverage will emit a gas that exerts a force in the direction to dislodge the stopper from the opening. On a hot day, the pressure could exert a force of between forty and fifty pounds. If the stopper is jammed into the opening with sufficient mechanical interference to resist such a high force, it will not be possible for the average consumer to remove the stopper at normal use temperatures. In the design of conventional easy-open metal can ends, it is assumed that the consumer can exert a force no larger than 8 pounds.
In co-owned U.S. patent application Ser. No. 08/953,067, now U.S. Pat. No. 6,220,470, a resealable closure is described that uses a sliding flap to unseal and later reseal the dispensing port of a container. This invention avoids the above problem by using a sliding motion that is nearly perpendicular to the primary vertical force generated by the internal pressure. There are two basic limitations with this design. The first is that, because of the creep tendencies of the plastic materials most suitable for such flaps, the flaps must be fairly thick in order to resist the forces generated by the internal pressure. The second is that the internal pressure creates a high friction force that resists the sliding of the flap.
The resealability problem has been solved for narrow neck bottles through the use of threaded bottle caps. Because of the mechanical advantage presented by the shallow angle of the threads, a moderate twisting force suffices to remove a cap that is strong enough to resist high internal pressures. With wider neck bottles, this type of closure is less successful. Although the same mechanical advantage principles apply, the force exerted by the gas pressure within the bottle is much higher. At a high beverage pressure, therefore, the friction force resisting the turning of the cap will be uncomfortably high. It is also well known that a threaded or lug closure on a wide mouth jar subjected to an external pressure (i.e. internal vacuum) can also be extremely difficult to open.
To reduce this friction force, it would be desirable to have a means to vent the pressure in the can or bottle prior to opening. There have been several inventions to achieve venting of the net internal pressure before full opening of a closure. Unfortunately, most of these inventions achieve the venting through the initial rotation of the closure. Such a venting means during the course of the rotation prevents a sudden and, possibly, dangerous missiling of the closure when the threads on the closure eventually clear those on the container. Because the closure must be rotated in order to vent the pressure, these designs cannot aid in reducing the force required for initial rotation.
It would be possible to provide a separate, small plug that would initially cover a venting port (for purposes of this disclosure, a venting port means a hole or other means of communication between the inside of the container and the outside environment.). This would require the consumer first to remove this small venting plug and then, in a separate action, remove the component that seals the dispensing port. It would be more desirable if the same action that initially vents the can could, when continued, open the dispensing port.
With current easy-open ends for metal beverage cans, one can vent and then open the end with the same lifting motion. In the initial portion of this venting, a small vent crack is created by fracturing a scored line in the panel. Unfortunately, this form of venting is non-reversible. Even if there were to be a means to reseal the main dispensing port, gas and liquid could still escape through this vent crack.
In each of the various embodiments of the present invention, a sealing flap is used to block a dispensing port of a beverage container in such a way that a pressure differential, i.e. the difference between the internal pressure of a beverage container and the surrounding atmosphere, enhances a seal of the dispensing port. For example, when the sealing flap is situated inside the container, i.e., under the lid of the container, and a sealing gasket is provided between the sealing flap and the perimeter of the dispensing port on the underside of the lid, the internal pressure of the container assists in forcing the sealing flap into a sealed engagement with the perimeter of the dispensing port.
In the embodiments of the present invention, it is desirable to use some type of physical interference to force the sealing flap into sealed engagement with the perimeter of the dispensing port. Once the sealing force is initiated by some type of physical interference, the carbonation within the beverage will gradually escape from the beverage and fill the head space beneath the lid, resulting in a build up of internal pressure. This creates a gradually increasing pressure differential, which enhances the seal between the sealing flap and the perimeter of the dispensing port. While it is recognized that the principles of the present invention can be applied to containers for non-carbonated beverages, and even to vacuum-packaged beverage and food containers, a particularly useful application of the present invention is for pressurized beverage containers, which are typically carbonated drinks.
In order to avoid exposing the surfaces that will contact the beverage or the consumer""s mouth to debris, it is also desirable to provide a movable dust cover on the outside, i.e., top, of the lid. Many of the embodiments of the present invention include such a dust cover. Advantageously, the external drive means of the resealable closure of the present invention provides a means to actuate the sealing flap between a sealed and an unsealed position, and also serves as the dust cover. It is also recognized that it would be advantageous to vent internal pressure of the beverage container prior to unsealing the dispensing port. This is because the internal pressure increases the force, including the friction force between the sealing flap and the perimeter of the dispensing port of the container lid, as well as between the sealing flap and other points of contact with the container. Once the internal pressure of the beverage container is vented, these resulting forces are substantially reduced, making it much easier to unseal the dispensing port.
A particular advantage of the present invention is that the forces necessary to initially vent the pressure in order to generally equalize the internal pressure with the surrounding atmospheric pressure are much lower in the various embodiments now disclosed, as compared to many conventional beverage containers, including bottles, because with these new resealable closures, venting is achieved prior to initial movement of the sealing flap. A further advantage is that any relatively high forces that must be exerted by a user on the external drive means in order to overcome the initial mechanical interference that had been used used to initiate the seal between the sealing flap and the perimeter of the dispensing port on the underside of the lid need only be exerted for a relatively short interval of time. This is an important improvement over beverage container lids that would require the user to exert high forces throughout the entire duration of travel of the drive means to overcome forces from mechanical interference.
In order to be able to achieve repeated re-sealing and re-opening of the dispensing port, and retain adequate pressure within the beverage container after re-sealing so that carbonated beverages will still be carbonated after being left to sit for extended periods of time, it is necessary not only to re-seal the dispensing port, but also to re-seal any venting means that are used to initially vent the internal pressure of the beverage container. In fact, if the vent is not re-sealed, liquid product could also flow through the vent when the container is resting on its side. While re-sealing of the venting means may take place after re-sealing of the dispensing port, it is most desirable if the venting means is re-sealed prior to, or at least during, re-sealing of the dispensing port, so that a user does not forget to re-seal the vent once the dispensing port is re-sealed. Alternatively, in embodiments where the venting means is closed subsequent to re-sealing of the dispensing port, it is desirable to provide a tactile and/or audible reminder that activates upon re-sealing of the venting means, such that a user is assured both the dispensing port and the venting means are re-sealed. The manner in which these and other features of the present invention are accomplished is explained in greater detail in the following Detailed Description of the Preferred Embodiments and the accompanying drawings.